The cause of the soil subsidence was believed to be because of the improper compaction of the sandy soils at the base of the trench and also potential inflow and infiltration into the clay pipe. The utility trench repair was needed and the soil needed to be stabilized and compacted to prevent further subsidence and roadway settlement.
The problems were also being exacerbated by the ever-increasing weight of the flexible pavement road. In order to relevel the roadway, the City would be forced to repave over the road and temporarily level it. The added weight only increased the subsidence, as the soils were not able to bear any additional loads. The City of La Quinta needed an innovative solution to complete this utility trench repair project.
Solutions and Results
1,170 linear feet of the the roadway and utility trench needed to be stabilized. In order to do this, the soils above the 15′ deep sewer line needed to be compacted and its weight bearing capacity needed to be re-established. Another part of the utility trench repair was to lift and level the roadway.
EagleLIFT utilized a chemical grout injection process to stabilize the soils and to lift the roadway back to grade. Through 5/8″ holes and metal tubes inserted 5′ and 10′ above the utility trench and at 3′ to the left and right of the center locations. Since the primary roadway settlement was occuring immediately above the trench the key was to densify and create upward movement in the center injection points.
The patterened injection method ensured that the soils would no longer subside and collapse into the trench. In summary, the entire 1,170 linear feet of the trench was stabilized in 7 working days and ahead of schedule. The flexible asphalt pavement was lifted and leveled and the work was completed in the daytime hours to reduce noise disruption.